1. Field of the Invention
The present invention relates to a welding solid wire with high feeding performance and arc stability on welding.
2. Description of the Related Art
Generally, from the viewpoint of improving the quality of a welded bead portion, arc stability on welding is important in a welding wire without regard to the kind of wire such as a solid wire, a flux cored wire or the like. Also, it is generally recognized that arc stability is closely related to feeding performance of the wire.
For example, Japanese Patent Laid-open Publication No. (Sho) 56-144892 discloses a solid wire plated with copper, which improves feeding performance by means of fluid lubricant retained within grooves which are formed on the surface of the wire, and by wet wire drawing work with grain boundary oxidation. Also, Japanese Patent Laid-open Publication No. (Hei) 5-1120 describes that arc stability of a wire may be obtained by performing wet wire drawing work of over one pass prior to plating work and improving adhesive performance of plating by cleaning the wire surface.
It has also been disclosed that improving the properties of lubricant used in wire drawing work stabilizes the feeding performance so that arc stability is improved.
Lately, for solid wires and flux cored wires, Japanese Patent Publication Nos. (Hei) 2-682806 and (Hei) 2-731505 disclose that arc stability is improved by forcing a reduction in the ratio of an apparent surface area calculated from the ratio of the substantial surface area to wire diameter.
It has also been disclosed in Japanese Patent Publication Nos. (Hei) 2-723793 and (Hei) 2-723799 that arc stability is improved by reducing impurities of over 0.2 xcexcm in diameter which adhere to and remain on a wire surface.
The prior art described above relate to properties and conditions of a wire surface.
First, the problems in feeding systems for wires will be considered.
FIGS. 1A and 1B show the feeding system for a copper plated solid welding wire, and particularly FIG. 1A and FIG. 1B represent systems using a wire reel and a pail pack, respectively.
A wire 6 is fed from a wire reel 1 or a pail pack 10 into feeding rollers 2 or 9. Then, before feeding to a tip portion 5 of a welding zone, the wire 6 in the wire reel 1 is fed through a guide tool 3 and a cable 4 and the wire 6 in the pail pack 10 is directly fed through the cable 4. Most of cable 4 has a bent portion X or Y and wire 6 contacts with the inner wall of the cable 4, resulting in large resistance which decreases the feeding performance. In addition, the reference numeral 7 in drawings indicates an arc forming a bead between weld zone and the end portion of the wire 6, and the reference numeral 8 indicates a power source.
In addition, referring to FIG. 2 which is a sectional view of the welding tip portion 5, the wire 6 is subjected to large resistance at contact points A, B and C of the inner wall of the tip portion, which affects the feeding performance of the wire.
In the case as described above, it is natural that the change of the properties of the wire surface should affect the feeding performance, i.e. stability of the arc 7 at the end portion of the fed wire 6. However, it is not clear whether the properties of the wire surface relate to the feeding performance. Thus, the matters noted above have required close examination.
As high efficiency for welding has been required lately and the feeding speed of wires tends to increase, higher arc stability is also required, but technical developments for arc stability have not progressed accordingly.
The present invention addresses the matters discussed above. It is an object of the present invention to provide a solid welding wire which has high arc stability by stabilizing the feeding performance of the wire upon welding.
It is another object of the present invention to provide a solid welding wire whose surface comprises copper plated film and which has high arc stability and high feeding performance upon welding
These and other objects will become apparent to one skilled in the art after having the benefit of the following disclosure.
The present invention is directed to an arc welding solid wire whose surface comprises copper plated film, wherein the elastic limit ratio of the finally produced wire is controlled in the range between 50 and 88%. The elastic limit ratio is defined as the ratio between elastic limit and tensile strength.
The elastic limit ratio is controlled by installing three to eight elastic limit ratio control vertical rollers and three to eight elastic limit ratio control transverse rollers. The elastic limit ratio control vertical and transverse rollers have a ratio D/d of 40 to 60, where xe2x80x9cDxe2x80x9d is roller diameter and xe2x80x9cdxe2x80x9d is wire diameter, and follow the coil control vertical and transverse rollers after final drawing of the welding solid wire whose surface comprises copper plated film.